Currently, caries including tooth fractures constitute about half of the causes of tooth loss, and removal of dental pulp is known to significantly increase the risk of tooth loss. The average lifetime of teeth is said to be 57 years at present. To enable a person to chew with the person's own teeth throughout life, the lifetime of teeth needs to be prolonged by 20 years or more. Despite the “8020” campaign (campaign for promotion of retaining at least 20 of one's own teeth at the age of 80), only 21% of present 80-year old people has achieved the goal. In order to achieve a 50%, a target set by the Japan Dental Association, drastic improvement in caries treatment is necessary.
The removal of dental pulp, i.e., pulp extirpation, causes loss of the reparative dentin forming ability and the defense mechanism against infection and loss of the alarm signal of pain, resulting in an increase in the risk of enlargement of the caries. In addition, there are no perfect methods for pulp extirpation treatment, and after pulp extirpation and root canal filling, a periapical lesion may be caused by leakage of the filler from a tooth crown side; or vertical fracture, aesthetic loss, or postoperative pain may occur.
Accordingly, in the super-aged society, it is very important to develop a new treatment for dental caries and pulpitis by regeneration of dentin and dental pulp incorporating technology of dental regenerative medicine in order to avoid unnecessary extirpation of the pulp and to prolong the lifetime of teeth.
Meanwhile, regarding the dental pulp regeneration, it is hitherto known that the dental pulp of a tooth with an immature root is regenerated by extracting the tooth, extirpating the dental pulp, treating the root canal, and then replanting the tooth. Furthermore, it is reported that even in a tooth with an immature root having a lesion in the apex portion, dental pulp-like tissue is regenerated by extracting the tooth, thoroughly enlarging and cleaning the root canal, and filling the cementum-dentin junction with blood clot, and completely sealing the cavity with mineral trioxide aggregate (MTA).
It is known that the dental pulp-like tissue of a canine healthy tooth with a mature root is regenerated by extracting a tooth, extirpating the pulp, resecting the apex portion or enlarging the apex portion at least 1.1 mm, replanting the tooth, and filling the apex portion with blood clot (Non Patent Literature 1).
Most of reports on the root canal dental pulp regeneration described above focus on teeth with immature roots, and it is not demonstrated that the tissue regenerated in a root canal is dental pulp intrinsic tissue having blood vessels and nerves. In addition, in all cases, teeth are extracted once, enlargement and cleaning of the root canals are performed in vitro, and the root canals are filled with blood clot after replantation.
A method for regenerating dental tissue by extracting a tooth to be treated, extirpating the pulp, and injecting a root canal filling material into the apex side of the root canal is also known, wherein the root canal filling material comprises cells including dental pulp stem cells and an extracellular matrix to which the cells including the dental pulp stem cells adhere (Patent Literature 1).
The dental pulp stem cells are advantageous in that they can be collected from deciduous teeth or wisdom teeth without much burden on patients. However, it is difficult to isolate a sufficient number of dental pulp stem cells from an elderly patient, and actual clinical application is thought to be difficult. Accordingly, in the super-aging society, it is preferable that dental tissue regeneration is realized using a cell source that can be more easily utilized.